1. Technical Field
The present invention relates to an illumination device and an electro-optical apparatus, and more particularly, to an illumination device which can be suitable for use in a display apparatus having an optical position detecting unit.
2. Related Art
Generally, in a display apparatus having an electro-optical apparatus, such as a liquid crystal display, there is a case where an illumination device such as a backlight is used in order to allow a display screen to be visually recognized or to achieve a high level of visibility. There is also a case where an indicating position detecting unit such as a touch panel is formed in the display screen of the display apparatus. In such a case, when specific positions on the display screen are indicated by a pen, a finger or the like, corresponding indicating positions are detected to be input to an information processing apparatus or the like.
As an example of the indicating position detecting unit (position coordinate input unit) such as the touch panel, there is known a capacitive or resistive touch panel which is configured to detect a contact state on the display screen in a mechanical and electrical manner. As another example, there is also known an optical touch panel in which a number of infrared light beams are caused to scan along the display screen, and photodetectors for detecting these infrared light beams are provided so as to correspond to corresponding one of the infrared light beams, so that when these infrared light beams are blocked by a finger or the like, the position coordinates of the finger or the like can be detected. Although a variety of types of optical touch panels are known, examples thereof are described in JP-A-2004-295644 and JP-A-2004-303172, for example.
However, in the above-mentioned optical touch panel, it is necessary to arrange a number of light sources, photodetectors, or optical switches, light guide structures, and the like in the vicinity of the display screen so as to correspond to the resolution of the position coordinates which are to be detected. Therefore, the number of optical elements increases, which may increase the manufacturing cost, and also increase the power consumption.